Solutions to both parts of the recursion learn lesson problem sets

part-1.py

@@ -4,17 +4,41 @@
 # the appropriate comment.
 
 # factorial
-
-
+def factorial(n):
+ if n < 0: 
+ raise ValueError
+
+ if n == 0: 
+ return 1
+
+
+ return n * factorial(n - 1)
 
 # reverse
-
-
+def reverse(text):
+ # base case
+ if len(text) <= 1: 
+ return text
+
+ # recursive case
+ length = len(text) - 1 
+
+ return text[-1] + reverse(text[0:length])
 
 # bunny
-
-
+def bunny(count):
+ if not count: 
+ return count
+
+ return 2 + bunny(count - 1)
 
 # is_nested_parens
-
+def is_nested_parens(parens): 
+ if not parens:
+ return True
+
+ if parens[0] == '(' and parens[-1] == ')':
+ return is_nested_parens(parens[1:-1])
+ else:
+ return False
 

part-2.py

@@ -4,13 +4,44 @@
 # the appropriate comment.
 
 # search
-
+def search(array, query): 
+ if not array: 
+ return False
+
+ if array[0] != query: 
+ array = array[1:]
+ return search(array, query)
+ else: 
+ return True
 
 
 # is_palindrome
-
+def is_palindrome(text): 
+ if not text or len(text) == 1: 
+ return True
+
+ if text[0] == text[-1]: 
+ return is_palindrome(text[1:(len(text) -1)])
+ else: 
+ return False
 
 
 # digit_match
-
+def digit_match(num1, num2):
+
+ if not num1 and not num2: 
+ return 1
+
+ else:
+ result = 0
+ last1 = num1 % 10 
+ last2 = num2 % 10 
+
+ if last1 == last2:
+ result += 1
+
+ if num1 // 10 == 0 or num2 // 10 == 0:
+ return result
+
+ return result + digit_match(num1 // 10, num2 // 10)